BIOL 252 1st Edition Lecture 4 Outline of Last Lecture I. Intro to Intracellular CommunicationII. How Action Potentials WorkIII. Refractory PeriodIV. Myelinated AxonsV. SynapsesOutline of Current LectureI. Cessation of the SignalII. Postsynaptic PotentialsIII. Neuronal CircuitsIV. Autonomic Nervous System (Visceral Motor Division)Current LectureI. Cessation of the Signala. How do we stop the signal?i. Diffusion: neurotransmitters can leak out of the synapse because there are no walls to contain themii. Re-uptake: done by pre-synaptic neuron1. SSRI: selective serotonin re-uptake inhibitors inhibit re-uptake, neurotransmitter stays in synapseiii. Degradation: enzymes breakdown neurotransmitters1. Acetylcholinesterase (AChE) breaks down AChII. Postsynaptic Potentialsa. In postsynaptic cell…i. Depolarization = EPSP, excitatory, can lead to action potential1.2. Multiple EPSP’s required to trigger action potentialThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.3.ii. Hyperpolarization = IPSP, inhibitory, can negate effects of other neurons1. Used if you want to prevent neurons from having action potentials2.III. Neuronal Circuitsa. Reverberatingi. Ex: control of respirationb. Divergingi. Ex: control of musclesc. Convergingi. Ex: sensory system (take in information, sent to the brain)IV. Autonomic Nervous System (Visceral Motor Division)a. Responsible for…i. Changing physiology of body for the flight or fight responseii. Returning it to state of rest/digestiii. Maintaining homeostasis: temperature, blood pressure, blood pH, ion balanceb. Poll Everywhere: Which system does not contain visceral structures? Skeletalc. Somatic vs. Viscerali. Visceral: cardiac and smooth muscle, glands (visceral targets)ii. Visceral neurons innervate smooth muscle & glands even if they are found in the ‘somatic’ part of the bodyd. Visceral Reflexes (Reflex Arc)i.ii. Visceral effector = autonomic nervous systemiii. Unconscious, automatic, stereotyped responses to stimulationiv. Example: blood pressure1. Baroreceptor in carotid artery lead to the brain2. If blood pressure is high, a signal is sent along nerve (glossopharyngeal – sensory visceral) and goes to the cardiac center3. Vagus nerve transmits inhibitory signal to cardiac pacemaker4. Example of negative feedback5.e. Neural Pathwaysi. Somatic motor1. All Myelinated, goes to somatic effectors2.ii. Visceral motor1. Myelinated preganglionic fiber goes to autonomic ganglion (ACh)2. => Unmyelinated postganglionic fiber => visceral effectorsa. ACh = parasympatheticb. NE = sympathetic3. Heart gets innervation from both parasympathetic and sympathetic and can distinguish between the two4. If heart has NE, it is speeding up because that is used by the sympathetic division5.f. Sympathetic vs. Parasympathetic Anatomyi. Sympathetic1. Short preganglionic neuron2. Thoracolumbar origin3. Innervates structures all over the body4. Postganglionic neurons travel to innervate smooth muscle and glands in the skin5. The adrenal medulla receives preganglionic neurons and itself actsas postganglionic neurons, releasing NE to the blood6.7.ii. Parasympathetic1. Long preganglionic neuron, ganglion on visceral target2. Craniosacral origin3. Innervates structures all over the body4. Cranial Nerves III, VII, IX, & X innervate visceral structures from thehead to the abdomen5. Pelvic Splanchnic Nerves (S2-S4) innervate the large intestine, rectum, bladder, & reproductive